In one of conventional apparatuses for generating sound, musical sounds are synthesized by using higher harmonics which are produced in frequency-modulation. One of the frequency-modulation methods is a feedback frequency-modulation method in which a sinusoidal wave produced in a sinusoidal table is fed back with a predetermined feedback ratio, and the sinusoidal wave thus fed back is controlled to have a predetermined phase difference to provide a sinusoidal wave having a predetermined waveform. The synthesized wave thus obtained is further controlled to have a predetermined envelope by an envelope generator.
In the conventional apparatus for generating sound, however, there are resulted in following disadvantages.
Firstly, it is difficult to generate various kinds of sounds. Especially, it is not easy to generate sounds such as rhythm sound-effects sound or effects sound-vibrato.
Secondly, it is difficult to change a waveform of output sound and store data of predetermined waveforms into a register. Further, a construction of the apparatus or software program becomes complicated in a case where a voice signal is produced in addition to an artificial sound produced by waveform data.
Thirdly, it is difficult to adjust a depth of modulation in frequency-modulation of output sound
Fourthly, it is difficult to generate far and near sound in accordance with simple software program.
Fifthly, it is difficult to generate sound of a predetermined waveform, although this is concerned with the second disadvantage.
Finally, it is difficult to divide a channel sound into left and right stereo sounds.